Earnings Per Share - Calculation of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Net income	$ 15,528	$ 15,253
Average Common Shares:
Basic (weighted-average outstanding shares) (in shares)	11,761	11,698
Dilutive potential common shares from stock options (in shares)	66	79
Diluted (weighted-average outstanding shares) (in shares)	11,827	11,777
Basic earnings per share (in dollars per share)	$ 1.32	$ 1.30
Diluted earnings per share (in dollars per share)	$ 1.31	$ 1.30